Phase separation and regrowth of aerosol matter collected after size fractionation in an impactor

Aerosol matter in the size range <2 μm was collected in a Berner impactor and subsequently analysed by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectrometry. Owing to the low electron beam energy of 5 keV (occasionally 10 keV), analysis was restricted to elements with atomic numbers 20 (Ca). Sub-micrometer aerosol matter was found to contain mostly S, O, and C as well as some K and Ca. Nitrogen appeared to escape detection, probably due to bombardment-induced sublimation of NO₃ and NH₄. During sampling at low to moderate relative humidity (<60%) the sulphur-rich fraction of the aerosol matter (most likely sulphates) regrew in the form of microcrystals with sizes up to 10 times larger than the mean aerodynamic diameter of the respective impactor stage. By contrast, when sampling during periods in course of which the relative humidity exceeded 70%, the aerosol matter regrew in the form of extended amorphous agglomerates. The aerosol deposits also contained large numbers of carbon nanoparticles, well separated from the regrown sulphate-rich matter. The nanoparticles were similar in size (20–40 nm), much smaller than the equivalent aerodynamic diameter of the impacting particles (63 nm–2 μm). Presumably, the carbon nanoparticles constituted the core of larger air-borne particles covered with sulphates (as well as with nitrates and organic carbon). The regrown microcrystals disappeared rapidly under electron bombardment at high current density, an observation that indicates high volatility at elevated temperatures. Aerosol matter collected in the size range between 1 and 2 μm contained large fractions of particles made of O, Si, P, K, and Ca (oxides). These particles were highly resistant to electron bombardment (hard) and showed little or no evidence for agglomeration or regrowth. After removing the soluble (acidic) material from the collected aerosol matter, only carbon nanoparticles and hard coarse particles were left behind. The observation of agglomerated or crystallized “soft” aerosol matter in combination with phase separation of carbon nanoparticles lends further support to the assertion that it is not possible to collect useful quantities of fine and ultrafine aerosol particles with as-suspended morphology. Some implications for health-related research are discussed.     

聚四氟乙烯微孔膜脱硫实验研究

采用聚四氟乙烯微孔膜脱除工业尾气中的SO2,研究了膜孔径、膜厚度、吸收液浓度、吸收流流速和进气速率等因素对脱硫效率的影响,为膜脱硫工业应用提供了参考数据。     

Source separation recycling schemes: A survey

Municipal waste arisings continued to increase during the 1970s in all the industrialized economies. Currently, in the midst of a severe international economic recession, the continuing escalation in the costs of waste disposal poses significant problems for municipal authorities. With the data constraints firmly in mind, this paper estimates the secondary materials supply potential of the municipal waste stream. The calculations suggest that a significant supply potential remains to be utilized despite ‘respectable’ overall recycling rates in most industrial economies. Resource recovery options can be divided into ‘low technology’ source separation schemes and ‘high technology’ mechanical separation schemes. The authors concentrate on the former option and appraise (on the basis of social cost-benefit analysis) a number of schemes that have operated in both Europe and North America.     

Urban waste recycling behavior: antecedents of participation in a selective collection program

ABSTRACT/ The aim of this study is to analyze the antecedents of urban waste recycling behavior. To achieve this goal, a concrete urban waste management program was chosen. The study focuses on the Selective Collection Program (SCP) in Zaragoza, a medium-sized city in northeastern Spain. The research starts with a conceptual model in which the variables that potentially affect recycling behavior can be classified into two groups: incentives and barriers. Moreover, the sociodemographic characteristics of the individuals are included in our study. Given that the proposed model requires specification of latent variables or constructs, the analysis is based on the Structural Equation Models (SEM) methodology. The results revealed that environmental awareness, knowledge of the environmental impact of urban waste, and the positive perception of management by local government exercise a positive effect on individual recycling behavior, while perceived personal difficulties (space and time availability) and distance to and from the container have a negative effect. As regards sociodemographic variables, this study found that annual family income sustains a negative relationship with recycling behavior, while age maintains a positive one. The results obtained clearly show the important role that the public authorities play, especially municipal governments, in achieving the waste recycling objectives established in accordance with international legislation.     

Simulated Limnological Effects of the Shasta Lake Temperature Control Device

We estimated the effects of a temperature control device (TCD) on a suite of thermodynamic and limnological attributes for a large storage reservoir, Shasta Lake, in northern California. Shasta Dam was constructed in 1945 with a fixed-elevation penstock. The TCD was installed in 1997 to improve downstream temperatures for endangered salmonids by releasing epilimnetic waters in the winter/spring and hypolimnetic waters in the summer/fall. We calibrated a two-dimensional hydrodynamic reservoir water quality model, CE-QUAL-W2, and applied a structured design-of-experiment simulation procedure to predict the principal limnological effects of the TCD under a variety of environmental scenarios. Calibration goodness-of-fit ranged from good to poor depending on the constituent simulated, with an R ² of 0.9 for water temperature but 0.3 for phytoplankton. Although the chemical and thermal characteristics of the discharge changed markedly, the reservoir's characteristics remained relatively unchanged. Simulations showed the TCD causing an earlier onset and shorter duration of summer stratification, but no dramatic affect on Shasta's nutrient composition. Peak in-reservoir phytoplankton production may begin earlier and be stronger in the fall with the TCD, while outfall phytoplankton concentrations may be much greater in the spring. Many model predictions differed from our a priori expectations that had been shaped by an intensive, but limited-duration, data collection effort. Hydrologic and meteorological variables, most notably reservoir carryover storage at the beginning of the calendar year, influenced model predictions much more strongly than the TCD. Model results indicate that greater control over reservoir limnology and release quality may be gained by carefully managing reservoir volume through the year than with the TCD alone. RID=" ID=" Author to whom correspondence should be addressed. e-mail: John_Bartholow&commat;USGS.gov     

A model recycling process for low density polyethylene

A dissolution/reprecipitation process has been developed for recycling low density polyethylene. In this paper model experiments on virgin material, either in the form of pellets or film for greenhouses, are presented. It is proposed dissolution of the plastic in an appropriate solvent, reprecipitation by means of non-solvents, washing of the material obtained and drying. The solvent mixtures involved are separated by distillation for further reuse. Toluene/acetone proved to be the most satisfactory solvent/non-solvent system. The recycled material was evaluated in terms of the following properties: melt flow index (MFI), crystallinity, mechanical performance in tensile mode and grain size analysis.     

火场残留助燃剂的提取分离及气相色谱/质谱分析

本文总结了从火灾现场提取样品中分离残留助燃剂的常用方法,比较了各种不同分离方法的优缺点及主要适用对象,并介绍了常见助燃剂的典型气相色谱/质谱图特性,为火灾调查识别的研究提供理论指导。     

水力旋流沉淀器在精对苯二甲酸废水处理中的应用

阐述了新型SXD水力旋流沉淀器的工作原理及结构特点，并从理论和实际应用两方面分析了影响水力旋流器处理效果的因素，评价了其在精对苯二甲酸废水处理中的性能。     

孤东油田含油污泥现状及处理技术

含油污泥是油田开发过程中的重要污染源,孤东油田目前对含油污泥主要采用自然干化填埋处理法。为了更好地回收原油,提高环境效益和经济效益,实验用离心分离法处理含油污泥,结果表明:使用该技术使油回收率可以达到80%以上。当含油量达到一定值时,会产生明显的经济、环境及社会效益。     

溢油分离回收的神妙武器

20世纪90年代以来,国内外在陆上和海域不断发生溢油事故,由此造成重大的资源损失和环境污染。文中介绍了欧美国家对此采取的应急措施和使用的应急装备,论述了日本世界化工股份公司溢油分离回收机的工作原理、结构特点和适用环境。